It said the boat, carrying 72 people including women, children and political refugees, ran into trouble after leaving Tripoli, the Libyan capital, for the Italian island of Lampedusa on March 25.

By the time the vessel drifted ashore at Zlitan, Libya, on 10 April, all but 11 passengers were dead, and another died after being imprisoned by forces loyal to Muammar Gaddafi, the country's leader.

The paper said the migrants used a satellite phone to call Moses Zerai, an Eritrean priest in Rome who runs a refugee rights organisation, who then alerted the Italian coastguard.

Witnesses told the paper a military helicopter appeared above the boat and lowered food and water, but flew off without a rescue boat arriving.

A survivor said the boat was later carried towards a Nato aircraft carrier, which the paper concluded was the French ship Charles de Gaulle.

But NATO spokeswoman Carmen Romero said the only aircraft carrier under the alliance's command at that time was the Italian ship Garibaldi.

"Throughout the period in question, the Garibaldi was operating over 100 nautical miles out to sea. Therefore, any claims that a NATO aircraft carrier spotted and then ignored the vessel in distress are wrong," she said.

"NATO vessels are fully aware of their responsibilities with regard to the International Maritime Law regarding Safety of Life at Sea and have already saved hundreds of lives at sea," she added.

Thierry Burkhard, spokesman for the chief of staff of the French armed forces, also denied the French navy had failed to help.

"The Charles de Gaulle was never at any moment in contact with this type of boat, nor [was] any other French vessel, due to its position," he said.

A spokesman for the Italian coastguard said the location of the ship was pinpointed with the help of satellite telephone providers and heading towards Maltese waters.

An alarm was sent from its Rome headquarters to all ships, civilian and military, in the area.

"If we had been in the area, we certainly would have intervened," said Lieutenant Massimo Maccheroni, adding that under maritime law, the coastguard cannot operate in other country's waters without permission.

Zerai told the Guardian the failure to rescue the migrants constituted a crime.

"There was an abdication of responsibility which led to the deaths of over 60 people, including children," he said.

"That constitutes a crime, and that crime cannot go unpunished just because the victims were African migrants and not tourists on a cruise liner."

Dozens of immigrants from north Africa have died attempting to reach Italian shores. On April 6, a boat carrying 200 people sank south of Sicily. In that case, Italian ships answered a distress signal and managed to save 50 people in Maltese waters.

The Guardian said those aboard the drifting boat included 47 Ethiopians, seven Nigerians, seven Eritreans, six Ghanaians and five Sudanese. Twenty were women and two were small children, one of whom was one year old.